Transmission line support



Oct. 25, 1955 c oy ET AL 2,721,362

TRANSMISSION LINE SUPPORT Filed Aug. 24, 1949 2 Sheets-Sheet 1 l '1 8; I (1? I I4 |Fc I 5! C! [4' e lcp Fig.3.

13' I 13' 9'w i I b a -9' Inventors; Robert L.Mc Coy, b Fred C. Vose,

/o *q T eir- Attofn ey.

Oct. 25, 1955 R. MCCOY ET AL 2,721,362

TRANSMISSION LINE SUPPORT Filed Aug. 24. 1949 2 Sheets-Sheet 2 Inventors: Robert L.Mc Coy, b Freci&C.VoseJ,

y WM

Their Attor ey.

United States Patent Ofiice Patented Get. 25, 1955 TRANSMISSION LINE SUPPORT Robert L. McCoy, Baltimore, and Fred C. Vase, Glen Burnie, Md, assignors to General Eiectric Company, a corporation of New York Application August 24, 1949, Serial No. 112,il36

7 Claims. (Cl. ar -e9 This invention relates to a transmission line support and more particularly to a transmission line support employing wood support poles and associated cross arms to support the transmission line conductors above ground.

The insulating properties of wood and its lower cost, as compared to metal, are factors which favor the use of wood in transmission line structures. Such factors tend to explain why wood support poles and cross arm assemblies are commonly used in preference to metal poles and towers to support transmission lines operating at what might be termed relatively low transmission line voltages, i. e., in the range up to 69 kv. For higher transmission line voltages, such as from 69 to 230 kv., it is found that the use of wood support poles and cross arms presents special problems which must be overcome if the support is to be satisfactory.

These problems are both mechanical and electrical. The mechanical problems are chiefiy concerned with supporting increased Weight. For example, for high voltages as compared to low, the transmission line conductors are larger, the insulator assemblies are heavier, and the conductors are spaced farther apart from each other and the support poles thus requiring that the weight of the conductors be carried at locations farther away from the support poles. An example of an electrical problem more troublesome at voltages in the range from 69 to 230 kv. is leakage current which flows through the wood cross arm to the support pole and then to ground. If contact is not made properly between the cross arms and support poles, local hot spots will develop which cause burning of the wood and consequent deterioration. Our invention is concerned with overcoming problems such as these and it is therefore a general object of our invention to provide an improved transmission line support employing wood poles and associated cross arms which is suitable for use at voltages up to, for example, 230 kv.

.One particular source of trouble in wood transmission line structure used heretofore is the manner in which the Wood cross arm is attached with respect to the wood support pole. This attachment is usually accomplished by employing a support fitting which may be simply a bolt and associated washers or it may include, besides the bolt, a bracket arrangement for supporting the cross arm. In either event, the bolt is located to extend through the cross arm and the pole in a direction such that the axis of the bolt is substantially at right angles to the longitudinal axis of the cross arm. This arrangement enables the cross arm to be tightened against the support pole by drawing up on the bolt. Either one or two cross arms may be employed and if two are employed the pole is normally located therebetween.

With this usual arrangement the weight of the cross arm bears directly on the through bolt, thus creating a concentrated stress location in the cross arm at the vicinity of the bolt which adversely limits the weight carrying capacity of the cross arm. Even by tightening up on the through bolt it is found difiicult to produce satisfactory contact between the cross arm and either the bracket to which it is attached or to the support pole itself, with the result that the support arrangement is susceptible to burning due to leakage currents. The foregoing comments apply equally well whether a single cross arm is being supported or whether two cross arms are being supported with the support pole therebetween.

A popular arrangement of the latter type is one employing two wood support poles and two parallel cross arms associated therewith so that the cross arms extend across the space between the poles and an equal distance beyond each pole. This arrangement gives the general appearance of an H and since it is desired to position the cross arms in parallel relation on opposite sides of the support poles, the arrangement is commonly referred to as a parallel plank H-frame construction. In practice, using through bolt fittings of the type described in the preceding two paragraphs, it is found difficult to position the cross arms in parallel relation because of the different diameters of wood support poles. One support pole may be several inches shorter in diameter than the other at the location where the cross arms are to be positioned. The way this is usually overcome is to notch the larger diameter pole sutficiently so that the cross arms may be drawn against the notched portion of this pole and against opposite sides of the smaller diameter pole and still be substantially parallel. This notching of poles, or gaining as it is called in the art, is a troublesome procedure and one that is especially difiicult to accomplish in the field.

Accordingly, it is another object of our invention to provide an improved fitting, and manner of forming the same, for attaching wood cross arms to wood support poles in a transmission line structure, this fitting being particularly advantageous in a parallel plank H-frame arrangement.

When the parallel plank H-frame type of transmission line support is used it is customary to support the insulator assemblies from insulator support fittings connected to the cross arms and located in the space between the cross arms. For the usual 3 conductor transmission line, three insulator support fittings are employed, one being located midway of the length of the cross arms and the other two being located adjacent opposite ends of the cross arms. Because it is difiicult to position the cross arms in true parallel relation, different sizes of insulator support fittings may have to be used in order to be able to connect the fittings to both cross arms and have them occupy the space between cross arms. In some instances adjustable width insulator support fittings have been employed but these are obviously more complicated, and hence usually more expensive, than a fixed width fitting. If, in practice, it was possible to be reasonably sure that the cross arms would be parallel at each support location the insulator support fittings could be of a standard size. In view of the fact that practical experience has shown parallel arrangement to be difiicult of attainment, it is common practice to stock a number of different hardware parts in order to be able to assemble the insulator support fitting in relation to the spacing which actually exists at a particular cross arm and pole assembly.

It is therefore another object of our invention to provide an improved insulator support fitting for a transmission line support employing wood support poles and associated cross arms.

In a preferred embodiment of our invention two wood support poles and two wood cross arms are used at each transmission line support location, the cross arms being positioned with respect to the support poles in accordance with the above-described parallel plank H-frame arrangement. To support the cross arms with respect to the support poles, we employ, at each pole, a support fitting which has ledges on which the cross arms rest. This fitting is sometimes referred to as a pole gain fitting and only the fitting, not the cross arms, is bolted to the support pole. At a particular pole, for example,

this fitting has a body portion which is bolted against the support pole and has on each side of this body portion a horizontal ledge for supporting a cross arm and a vertical flange against which the inner side of the cross arm abuts and to which the cross arm is bolted. Since the support fitting is the only part which is bolted to the pole, it is not necessary to disconnect the fitting from the pole in order to remove either one or both cross arms. Instead, it is necessary only to unbolt the cross arm from the fitting thus facilitating replacement of cross arms.

In order to support the insulator assemblies from the cross arms, we employ fittings, each in the form of a reinforced channel-shaped bracket, which may be used interchangeably at the center or at the ends of the cross arms. This interchangeability is derived from the fact that by means of the fittings for attaching the cross arms with respect to the support poles, the cross arms are maintained a predetermined distance apart and in parallel relation and hence it is possible to use an insulator support fitting of uniform size to connect between the cross arms. This insulator support fitting is so constructed that by positioning it at 90 with respect to the position it occupies at the center of the cross arms, it can be used at the ends of the cross arms to support the insulator assemblies from the very ends of the cross arms, thus giving maximum spacing between the transmission line conductors for a particular length of cross arm.

Other objects and advantages of our invention will ecome more apparent from the following detailed description taken in conjunction with the attached drawings in which Fig. l is a perspective view of a transmission line support employing a pair of support poles and parallel cross arms attached with respect thereto in accordance with an embodiment of our invention; Fig. 2 is a perspective view of a pole gain fitting adapted to be used in the assembly illustrated in Fig. i; Fig. 3 is a plan view of a blank from which the fitting illustrated in Fig. 2 may be formed; Fig. 4 is a perspective view of an insulator support fitting adapted to be used in the assembly illustrated in Fig. 1; Fig. 5 is a plan view of a portion of the assembly shown in Fig. 1, portions of members shown in Fig. 5 being broken away to shorten the figure; Fig. 6 is a side elevation view of the assembly shown in Fig. 5; Fig. 7 is an end view of the assembly shown in Figs. 5 and 6; and Fig. 8 is a sectional view taken on line 38 of Fig. 5.

In a preferred embodiment of our invention, as illustrated in Fig. 1, two upright wood support poles 1 and two wood cross arms 2 are positioned with respect to each other so that the cross arms are parallel and extend across the space between the support poles and beyond this space as shown in Fig. 1. As previously mentioned, this particular arrangement of the wood support structure is referred to in the art as a parallel plank H-frame arrangement. Such an arrangement is especially desirable from the standpoint of mechanical strength for supporting transmission line conductors operating at voltages above 69 kv.

Again referring to Fig. 1, the cross arms 2 are supported in parallel relation i. e. in registration with each other, with the support poles 1 therebetween as shown in this figure, by means of plate member fittings 3. These fittings maintain the cross arms 2 a fixed distance apart in a manner described more in detail later in this specification. By means of the fittings 3 the cross arms 2 are supported not only in correct relation with each other but are also firmly supported with relation to the support poles l.

The three transmission line conductors 4 are held in suspended position above the ground by suitable means,

not shown, attached to the ends of insulator assemblies 5. These insulator assemblies are, in turn, supported from the parallel cross arms 2 by means of insulator support fittings 6. The positioning of the insulator support fittings is such that one fitting is placed midway of the length of the cross arms 2 and the other two fittings are placed at the ends of these cross arms as shown in Fig. 1. This is done to attain proper weight distribution and proper spacing between the transmission line conductors 4 for the through line arrangement shown. As is mentioned in greater detail hereinafter, the insulator support fittings 6 are constructed so that the outermost insulator assemblies are suspended from the very ends of the parallel cross arms 2, thus utilizing the entire length of these cross arms for spacing purposes. This naturally enables maximum conductor spacing to be obtained for a given length of cross arm.

Referring to Fig. 2 of the drawings, a form of support fitting for supporting and attaching the cross arms 2 with respect to the support poles 1 is shown in greater detail. This particular fitting is often referred to in the art as a pole gain fitting and is sometimes referred to in this specification as such a fitting. It comprises a plate member having a substatnially flat body portion 7 which forms a connecting web between inturned flanges 8 and support ledges 9. The body portion 7 includes a slightly curved center pole engaging section or portion 10 which enables the fitting 3 to seat properly against the convex outer surface of a support pole, and parallel ribs 3'7 which are formed in the body portion 7 and which strengthen the body portion against buckling between flanges 8. The inturned flanges 8 are spaced apart equally from and are symmetrically disposed with respect to the curved center portion 16 and provide flat surfaces which the inner sides 11 of the cross arms 2 may engage. When these cross arms are positioned against the flanges 8 in the manner just described they may be drawn firmly against the outer surfaces of these flanges, such a surface being designated at 12, thus afliording good contact and minimizing the likelihood of wood burning because of leakage currents at this support location. As was mentioned earlier in this specification, wood burning at the location where the cross arm is attached to the support pole is a problem in this art. With the construction just described, a large area of contact is afforded whereby low resistance to leakage currents is presented and, consequently, the likelihood of burning is decreased.

The manner in which support ledges 9 are positioned with respect to facing flanges 8 is such that the lower edge of a cross arm can rest firmly upon a support ledge and, at the same time, the inner face 11 of the cross arm can press firmly against the outer surface 12 of an inturned flange member 8. In other words, a flange 8 and a ledge 9 are positioned at right angles to each other with the flange being substanially in alignment with the inner edge of the ledge, i. e., an edge such as 40 shown in Fig. 2. In effect, the support ledge extends inward from an edge of the body portion 7, as for example, edge 39 shown in Fig. 2, toward the pole engaging section 10 and the body portion is stepped in above the ledge whereby the cross arm can be seated perpendicular to the body portion. Of course, each flange 8 can be considered as extending from a stepped in portion of the body portion 7. Each of the flanges 8 contains a pair of elongated slots 13 and 14, the purpose of which is described later in the specification.

The fitting shown in Fig. 2, and described immediately above, may be formed from a metal blank such as is shown in Fig. 3. This blank, designated generally by the numeral 3', is fiat and substantially rectangular in shape with lower corner portions of the blank being cuta-way as shown in Figure 3 since it is not necessary for the ledges 9 to be as wide as the inturned length of flanges 8. Preliminary to other forming operations, slots 13' and 14 and bolt receiving openings 35' and 36' may be punched out of the blank 3 at locations as shown in Figure 3. The blank 3 is preferably a piece of steel of suitable strength to serve the purpose. A piece A" thick is considered satisfactory for most applications.

In order to free portions of the blank for bending, the blank is out along the solid lines a and 1) shown in Figure 3. Portions 8 are then bent or struck up out of the plane of the paper and along the dotted lines 0 to form flanges 8. Likewise, portions 9 are bent or struck up out of the plane of the paper and along the dotted lines d to form ledges 9. Portions 8 and 9' are struck up sufiiciently so that they are substantially at right angles to the body portion 7" and to each other. Following the cutting and bending operations, or prior thereto if desired, the body portion 7 can be bulged up, out of the plane of the paper and with the center line of the bulge being along dotted line e, to form the curved portion shown in Figure 2. Similarly, the parallel ribs 37 are formed so that the fitting in its final shape, as shown in Fig. 2, will have increased strength against buckling between the flanges 8.

Fig. 4 discloses a fitting 6 which may be used to support the insulator assemblies 5 from the cross arms 2. This fitting 6 is channel-shaped, having a channel back member and similarly shaped channel sides 16. The sides 16 are braced with respect to the back portion 15 and with respect to each other by means of a generally Y shaped brace member 17. The upper end portions 18 of the brace 17 are connected to the inner surfaces of the side members 16 of the fitting by suitable means, such as being welded thereto and the lower stern portion 19 of the brace is likewise connected to the back 15 of the fitting substantially centrally of the inner surface of this back member. Adjacent the stem portion 19, a substantially rectangular through slot 20 is formed in the back member 15. The purpose of slot 20 is to accommodate ahanger strap for connecting the center insulator assembly 5 to a fitting 6, as Will be described in greater detail hereinafter.

For a more detailed consideration of the manner of attaching and supporting the cross arms 2 with respect to the support poles 1, reference is made to Figs. 5 and 6 of the drawings. As will be readily appreciated from an inspection of these figures, they show portions of the right half of the structure shown in Fig. 1, the center insulator support fitting 6 being included in these figures, and the cross arms 2 being shortened in order to obtain greater detail in the figures. The arrangement of the various parts in the left half of the structure shown in Fig. l is the same as for corresponding parts in the right half of this structure and consequently a further detailed showing of the left half of the structure shown in Fig. 1 has been omitted because it would be merely duplicative of what is shown in Figs. 5 and 6.

In Fig. 5 the spacing between cross arms 2 corresponds to the diameter of the support pole 1 shown there. This particular diameter pole will, in actual practice, be the largest diameter pole to be used for this particular spacing but smaller diameter poles may be used because the pole gain fitting 3 supports the cross arms 2 a fixed distance apart regardless of whether the diameter of the support pole l is smaller than that shown in Fig. 5. In practice it is found that the diameters of support poles at cross arm locations may vary from 8 to 12'. By dimensioning our support fitting 3 to accommodate the larger diameter pole we avoid the necessity of having to notch or gain this pole as is usually necessary when two different diameter support poles are encountered at a particular support location. Yet we can also use the same fitting at the smaller diameter pole.

The manner in which the fixed spacing between cross arms is obtained is readily appreciated from an inspection of Figs. 5 and 6 wherein it can be seen that the cross arms 2 are maintained a fixed distance apart by the inturned flanges 8 of the fitting 3. The distance between these flanges can be predetermined to accommodate the maximum support pole diameter likely to be encountered in the field. If smaller pole diameters are encountered, this will not affect the cross arm spacing because the fitting is attached to the pole, not by a bolt which extends at right angles to the cross arms, but by bolts which extend parallel to the cross arms. Again referring to Figs. 5 and 6, the bolts 21 secure the fitting 3 firmly against the support pole 1, said bolts extending through the openings 35 and 36 in the curved portion 10 of the fitting and being tightened against plates 22 which are positioned on the opposite side of the pole from the fitting 3. The lower bolt opening 36 is elongated sideways, as shown in Figs. 2 and 3, to provide flexibility in positioning the fitting 3 with respect to the support pole 1 so that the ledges 9 will be substantially horizontal. The curved portion 10 of the fitting readily accommodates the convex pole surface adjacent thereto and thus provides firm engagement between the fitting and pole. A further important advantage obtained from this manner of attachment of the fitting 3 to the support pole 1 is that the bolts which carry the weight of the cross arms 2 do not extend through these cross arms. Consequently the weight of the cross arms does not bear directly on bolts but, instead, bears on larger area ledges thus better distributin the stresses over the entire cross section of the plank arms resulting in additional developed strength in a given size arm.

Each cross arm 2 is attached to the support fitting 3 at a particular support pole 1 by being connected to a flange 8 of the fitting. A preferable connecting member is a bolt which extends through the cross arm, midway of the height of the cross arm, and is received by either slot 13 or slot 14 in flange 8 depending on which of these slots is substantially midway of the height of the cross arm. In Figs. 5 and 6, the bolt 23 is shown as. being received in slot 13 and the cross arm 2 is of such height that slot 13 is substantially midway of the height of the cross arm. However, because slot 14 is also available for use, it is possible to attach cross arms having a greater height than those shown in Figs. 5 and 6. In this instance, of course, the height of the cross arm is such that slot 14 is substantially midway of the height of the cross arm. It is desired to bolt the cross arm to flange 8' substantially midway of the height of the cross arm because this manner of bolting provides a better attachment than if the bolt were of]? center. The provision of two bolt receivin slots in each flange enables the same fitting to be used for two different heights of cross arms and still attain this object. This facilitates interchange of cross arms.

The slots 13 and 14 are elongated in order to provide ample tolerance for bolting conditions encountered in the fl'el'd, the length of the slots making it easier for them to receive the attaching bolts. When a cross arm 2 is bolted to a flange S, the inner surface 11 of the cross arm abuts firmly against the outer surface 12 of the flange and the lower surface 11 of the cross arm rests on ledge 9 which bears all of the vertical loads since the slots are so located to match with holes in the wood members so that bolts through the slot and hole in the cross arm will not support vertical loads on the cross arm.

The use of one attaching bolt 23 to secure a cross arm 2 to a particular inturned flange 8 and to maintain the cross arm firmly seated on a particular support ledge 9 facilitates easy removal of the cross arm from the supporting fitting 3 without requiring dismantling of the other cross arm or requiring dismantling of the fitting 3 from the support pole 1. Insofar as removing a cross arm from support fitting 3 is concerned, it is necessary to remove only the attaching bolt 23. This is in contrast to assemblies using a through bolt which extends at right angles to the cross arms and through the support pole because in such arrangement when the bolt is removed both cross arms are loosened from the support pole.

Obviously, our invention also facilitates replacement of individual poles.

As has been stated, the insulator support fittings 6 are interchangeable from end to center of the cross arms and vice versa. This may be observed from Figs. and 6 wherein the insulator support fitting 6 is shown in one position at the center location of the cross arms and yet another position at one end of the cross arms.

Considering the end location first, it is seen that the back member of the insulator support fitting 6 extends across the space between cross arms 2 at the very end of these cross arms. The sides 16 of the fitting are firmly attached to the inner sides 11 of the cross arms 2 adjacent the ends of these cross arms by means such as bolts 24% which extend through openings 25 in the sides 16 and are tightened by means of associated nuts and washers. To secure adequate strength, four bolts are employed to connect each side member 16 and the adjacent end portion of the cross arm 2 is additionally reinforced by plates 26 and through bolts 27, in the manner illustrated in Figs. 57.

Referring to Fig. 7, a hanger strap 28 is shown which is used to attach the insulator assembly 5 to the insulator support fitting 6. This strap 23 is attached to the back portion 15 of the insulator assembly by means such as bolts 29. Two bolts are employed in the construction illustrated and the bolt receiving openings 39 in the back plate 15 are aligned so that the strap 28 hangs vertically when the strap is bolted to the back plate 15 of the insulator support fitting 6. The hanger strap is thus at the extreme end of the cross arms and hence the end insulator assembly 5 is positioned to obtain maximum spacing between transmission line conductors. A V brace may be connected to the fitting 6 at the upper hole 30, if desired.

This same type of insulator support fitting 6 is utilized to support the center insulator assembly 5 by attaching the support fitting 6 to the cross arms 2 in such a manner that the back portion 15 of the fitting occupies a position 90 displaced from that occupied by it at the ends of the cross arms. For example, referring to Figs. 5 and 8, it will be observed that the brace 17 is in upright position with respect to the cross arms and that the back portion 15 of the fitting 6 extends between the cross arms adjacent the lower edges 11' of these cross arms. Again, the sides 15 of this fitting 6 are attached to the inner sides 11 of the cross arms 2 by means of bolts 31 which extend through the openings 25 in the sides 16 and which are tightened by means of associated nuts and washers to maintain the fitting 6 securely in position with reference to the cross arms. Reinforcing plates 38 are held against the outer sides of the cross arms by the bolt assemblies 31.

The center insulator assembly 5 is supported by a strap member 32 which is attached to brace 17 and which extends through the slot 20 in the back portion 15 of fitting 6. This strap 32 is maintained in vertical position by means of a pair of attaching bolts 33 which extend through vertically aligned openings 34 in brace 17. The strap 32 is the same size and shape as the strap 28 and may be used interchangeably therewith. Likewise, a V brace may be connected to the center fitting at the upper hold 34, if desired.

From this discussion it will be appreciated that the construction of fitting 6 enables this fitting to be used either at the center or ends of the cross arms 2 and obviously this reduces the number of different parts needed to make up the transmission line support assembly. It is possible to utilize this fitting interchangeably because the pole gain fittings 3 maintain the cross arms 2 in fixed spaced parallel position. Furthermore, the fitting 6 may be used with difierent height cross arms because there is no lip member on the fitting which restricts it to use with a fixed size cross arm, i. e., there is 8 no lip member which must engage the top of the cross arm.

To illustrate the relative dimensions of various parts of our transmission line support structure, an example is given of an installation designed to support a three phase line operating at 132 kv. In this installation two wood support poles and two wood cross arms are used at a typical support location and the poles and cross arms are arranged in parallel plank H-frame arrangement. The wood support poles should be not more than 12 in diameter at the location above ground where the cross arms are to be positioned. Each cross arm is 32 feet long to provide a 16 foot space between adjacent transmission line conductors. Additionally, each cross arm is 3%" wide and 9 /2 high.

The pole gain fitting is a piece of galvanized steel A" thick dimensioned to provide a 12 space between cross arms. Each cross arm rests on a ledge 3% wide, to support the 3 /8 width of the cross arm, and 2 /8 long. Each cross arm also rests against a flange 4 /2 wide and 7 /2 high. This flange is slotted so that the cross arm can be bolted to the flange midway of the 9 /2" height of the cross arm. The pole gain fitting includes a curved surface adapted to contact the convex surface of the support pole and the fitting is bolted to the pole by two bolts which are parallel to the long axis of the cross arms. There is about 46 sq. inches contact between the pole gain fitting and the support pole and about 36 sq. inches of contact between this fitting and each cross arm. These contact areas provide safety against burning of the wood due to leakage currents.

The insulator support fitting is formed of galvanized steel, of #3 gauge for the back and sides of the fitting and of #7 gauge for the internal brace. The back is 12" long and 7" wide and each side is 7" x 7". To attach all fittings to the cross arms /3" bolts may be used throughout and 4" bolts may be used to connect the pole gain fitting to the pole.

For transmission line voltages other than 132 kv. dimensions of cross arms and fittings will be varied, as will be apparent to those skilled in the art, to accommodate the particular voltage for which the line is designed. While in the example just given, as well as through the preceding part of this patent specification, the pole gain fitting 3 has been described for use in a parallel plank H-frame structure, this particular fitting may obviously be employed to support one cross arm with respect to one support pole, two cross arms with respect to one support pole, one cross arm with respect to two or more support poles or even two cross arms with respect to two or more support poles. Two of the pole gain fittings may be used at each support pole to provide additional strength and when so used the fittings may be positioned opposite each other to provide four ledges 9, said ledges being positioned so as to provide a pair of ledges to support each cross arm at one support pole. Insofar as use of the pole gain fitting 3 is concerned, such modifications as these are considered to be within the scope of our invention.

When the pole gain fitting 3 is employed to support one cross arm with respect to one or more support poles, it provides the advantages of ready detachability of the cross arm from the fitting without requiring the fitting to be detached from the support pole, avoids having the weight of the cross arm carried on a bolt which extends through the cross arm and the support pole, and provides ample contact surfaces between the cross arm and fitting, and between the fitting and support pole, to pass leakage currents. When the pole gain fitting 3 is used in a parallel plank H-frarne arrangement, it provides the additional advantages of maintaining the cross arms in fixed spaced position without requiring notching or gaining of the support poles to accomplish this, and also makes it possible to use interchangeable insulator support fittings 6 to support the insulator assemblies and obtain maximum spacing between the transmission line conductors for a given length of cross arm.

While we have described and illustrated a preferred embodiment of our invention, we wish it to be understood that we do not intend to be restricted solely thereto but that we do intend to cover all modifications thereof which will be readily apparent to those skilled in the art and which come within the spirit and scope of our invention.

What We claim as new and desire to secure by Letters Patent of the United States is:

1. A fitting useful in a transmission line structure for supporting two cross arms in registration on opposite sides of an upright support pole, said fitting comprising a plate member having a substantially flat body portion including a curved pole engaging center section adapted to engage said pole to position said body portion in substantially upright position, oppositely disposed parallel flanges extending from said body portion and being symmetrically disposed with respect to said pole engaging section, said body portion extending between said flanges and being discontinuous beyond said flanges, support ledges also extending outward from said body portion, there being a support ledge associated with each flange and said support ledge extending from a location below said flange and at right angles to said flange and in a direction away from the center of said body portion whereby a cross arm may be positioned on said support ledge and contacted laterally by said flange.

2. A transmission line support comprising two upright parallel spaced wooden rod-like support poles and two horizontally disposed parallel spaced wooden plank-like cross arms positioned in an identical horizontal plane, said arms disposed on opposite sides of said poles and straddling said poles whereby said poles are disposed between said arms, said arms supported from said poles by single piece integral metallic brackets having generally flat body portions, the central portions of said body portions being concavely curved, said brackets positioned between said arms and said concavely curved central portions engaging convexly curved other sides of said poles, said brackets rigidly and immovably but detachably connected to said poles by bolts extending through said concavely curved central portions and poles parallel to said arms, the opposite ends of said brackets on opposite sides of said concavely curved central portions adjacent the opposite inwardly facing sides of said plank-like cross arms having vertically disposed parallel flanges integrally formed thereon extending perpendicular to said flat body portions, said flanges extending parallel to and making flat surface engagement with said inwardly facing sides, said arms rigidly and immovably but detachably connected to said flanges by other bolts extending through said arms and flanges and spaced from said holes, the two flanges of each of said brackets spaced from each other by an equal predetermined distance not less than the diameters of said p'oles adjacent said brackets whereby said flanges will retain said arms in spaced parallel relationship even though one of said diameters is less than the other of said diameters, and means for relieving said other bolts from carrying the full weight of said arms and transmission lines connected thereto comprising outwardly extending and horizontally disposed ledges integrally formed on said opposite ends of said brackets, said ledges making fiat surface engagement with the bottom edges of said plank-like cross arms.

3. A transmission line support comprising an upright wooden rod-like support pole and two horizontally disposed parallel spaced wooden plank-like cross arms positioned in an identical horizontal plane, said arms disposed on opposite sides of said pole and straddling said pole whereby said pole is disposed between said arms, said arms supported from said pole by at least one upright single piece integral metallic bracket having a generally rectangular-like body portion, the upper portions of opposite side ends of said rectangular-like body portion having vertically disposed parallel flanges integrally formed thereon perpendicularly to said rectangular-like body portion, said bracket disposed between the inwardly facing opposite sides of said plank-like cross arms and said flanges making flat surface engagement with said inwardly facing opposite sides, said body portion engaging another side of said pole and said flanges extending away from said pole, said bracket rigidly and immovably but detachably connected to said pole by at least one boltlike member extending through said body portion and pole parallel to said arms, said flanges spaced from each other by a predetermined distance not less than the diameter of said pole adjacent said bracket whereby said bracket will retain said arms in parallel spaced relationship with respect to each other by a distance equal to said predetermined distance even though said diameter is less than said predetermined distance, said arms rigidly and immovably but detachably connected to said flanges by other bolt-like members extending through said arms and flanges and spaced from said pole, and means for relieving said other bolt-like members from carrying the full weight of said arms and transmission lines connected thereto comprising horizontally disposed outwardly extending ledges integrally formed adjacent the lower portions of opposite side ends of said rectangular-like body portion, said ledges extending below said cross arms and making fiat surface engagement with the bottom edges thereof.

4. A metallic channel-shaped bracket for supporting two parallel spaced horizontal wood plank-like cross arms along opposite sides of an upright wood rod-like support pole, said channelshaped bracket having two spaced parallel side portions integrally connected to a base portion and perpendicularly extending from a same side of said base portion, a central part of said base portion being bulged towards said side portions whereby an opposite side of said base portion along said bulged central part is concavely curved, the axis of said concavely curved opposite side central part extending parallel to said side portions, said concavely curved opposite side adapted to engage a convexly curved other side of said rod-like support pole whereby said side portions will be vertically disposed adjacent said opposite pole sides, and a pair of horizontally disposed support ledges integrally connected to said base portion extending outwardly of said base portion beneath and beyond said vertically disposed side portions adjacent to said opposite pole sides.

5. In a transmission line conductor support comprising a pair of upright parallel spaced support poles and two parallel spaced horizontal cross arms, disposed on opposite sides of said poles in registration with each other whereby said poles are disposed between said arms, single piece integral support fittings mounted on said poles, said support fittings having body portions thereof disposed between said arms perpendicularly thereto, said body portions rigidly and iminovably connected to other sides of said poles by bolts extending parallel to said arms, said support fittings having supporting ledges engaging the lower edges of said cross arms for supporting said cross arms and spaced oppositely disposed flanges engaging the inwardly facing sides of said cross arms to maintain said cross arms a predetermined distance apart irrespective of whether the diameter of either or both of said support poles at the cross arms location is less than said predetermined distance, said arms connected to said flanges by other bolts spaced from said support poles.

6. A fitting useful in a transmission line structure for supporting a pair of parallel spaced horizontal cross arms with respect to opposite sides of an upright support pole, said fitting comprising a plate member having a substantially flat generally rectangular body portion including a central pole engaging section adapted to engage another side of said pole to position said body portion in substantially upright position, a supporting ledge extending substantially horizontally inward from each of the lower portions of the side edges of said body portion toward said pole engaging section when said body portion is positioned in substantially upright position, said body portion being stepped in above each of said supporting ledges, and a substantially vertical bracing flange extending from each of the stepped in parts of said body portion, said flanges being positioned substantially in alignment with the inner edges of said supporting ledges and being adjacent thereto whereby a pair of parallel spaced horizontal cross arms may be positioned on said supporting ledges and be contacted laterally by said bracing flanges on said opposite support pole sides.

7. A fitting useful in a transmission line structure for supporting a pair of parallel spaced horizontal cross arms on opposite sides of an upright wood support pole, said fitting comprising a metallic plate member having a substantially flat generally rectangular body POLUOIJ including a curved pole engaging section between opposite side edges thereof adapted to engage another side of said pole to position said body portion in substantially upright position, a supporting ledge extending substantially horizontally inward from adjacent the lower portions of each of said opposite side edges toward said pole engaging section when said body portion is positioned in substantially upright position, said body portion being stepped in above each of said supporting ledges, and a bracing flange extending from each of the stepped in parts of said body portion, said flanges being positioned at right angles to said supporting ledges and substantially in alignment with and adjacent to the inner edges of said ledges whereby said pair of parallel spaced horizontal wood cross arms may Add be positioned on said supporting ledges and be contacted laterally by said bracing flanges on said opposite sides, said bracing flanges having a plurality of vertically spaced bolt receiving slots therein for connecting different sizes of cross arrns individually in seated position on said supporting ledges.

References tlited in the file of this patent UNITED STATES PATENTS 933,067 Ferry Sept. 7, 1909 958,933 Love May 24, 1910 1,032,715 Walker July 16, 1912 1,099,612 McEWen June 9, 1914 1,100,822 Gordon June 23, 1914 1,139,487 Cangia May 18, 1915 1,316,952 Haydon Sept. 23, 1919 1,346,955 Gustafson July 20, 1920 1,690,392 Austin Nov. 6, 1928 1,692,806 Barnett Nov. 27, 1928 1,761,509 Williams June 3, 1930 1,865,765 Kelley July 5, 1932 1,876,580 Austin Sept. 13, 1932 1,885,318 Austin Nov. 1, 1932 2,045,150 Kenneally June 23, 193 2,182,660 Dillard Dec. 5, 1939 2,241,212 Mack May 6, 1941 2,276,391 Hathorn Mar. 17, 1942 2,333,519 Callander Nov. 2, 1943 FOREIGN PATENTS 459,376 Great Britain of 1937 

